The present invention relates to an optical wave coupler and is more particularly directed to an evanescent wave coupler that uses an interleaved film.
It is known in the art to fabricate optical wave couplers particularly applicable to fiber optics. Such devices typically involve removal of the cladding material from two optical fibers by acid etching in a solution of hydrofluoric acid, or by the use of abrasive papers or pastes. The cladding is removed until about one micrometer of cladding remains over each of the fiber optic cores. The fibers prepared in such a manner are then placed in optical contact with their etched or ground surfaces touching. Such assemblies position the fiber optic cores within about one to three micrometers apart. This distance is close enough to permit coupling of optical energy from one fiber core to the other.
The difficulties with acid etching or abrasively wearing away the cladding material surrounding the fiber cores is the ability to know when to stop the etching or abrasion process since the location of the core only becomes evident after the removal process has penetrated the core. If the core is reached, evanescent coupling is not possible by the above described prior art fabrication techniques.
A need has been felt to achieve consistent evanescent coupling fabrication. The amount of coupling between the two fibers is a function of the distance between the two fiber cores. If an assembly could be built which would yield consistent evanescent coupling assemblies such devices could be used for pressure sensing systems, e.g., microphones, hydrophones, transducers, etc.